

*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
    font-family: 'Poppins' sans-serif;
}

html, body{
    display: grid;
    height: 100%;
    place-items: center;
    background: #000;
    overflow: hidden;
}

button{
    position: relative;
    height: 60px;
    width: 200px;
    margin: 0 35px;
    border-radius: 50px;
    border: none;
    outline: none;
    background: #111;
    color: #fff;
    font-size: 20px;
    letter-spacing: 2px;
    text-transform: uppercase;
    cursor: pointer;
}

button:first-child:hover{
    background: linear-gradient(90deg, #03a9f4, #f441a5,  #ffeb3b, #03a9f4);
    background-size: 400%;
}

button:last-child:hover{
    background: linear-gradient(90deg, #fa7199, #f5ce62,  #e44360, #fa7199);
    background-size: 400%;
}
button:first-child::before,
button:last-child::before{
    content: "";
    position: absolute;
    background: inherit;
    top: -5px;
    right: -5px;
    bottom: -5px;
    left: -5px;
    border-radius: 50px;
    filter: blur(20px);
    opacity: 0;
    transition: opacity 0.5s;
}

button:first-child:hover::before,
button:last-child:hover::before{
    opacity: 1;
    z-index: -1;
}

button:hover{
    z-index: 1;
    animation: glow 8s linear infinite;
}

@keyframes glow{
    0%{
        background-position: 0%;
    }
    100%{
        background-position: 400%;
    }
}